Field of the Invention
This invention relates to visual depth perception in two dimensional pictures, and displays, including electronic generated ones.
There are two methods to perceive depth both in real life scenes and in pictures, a stereoscopic perception of depth and a psychological perception of depth. Stereoscopic depth perception requires the observer to use two eyes whereas psychological depth perception can be experienced by the use of just one eye.
Stereoscopic depth perception requires that the observer view a real life scene from two different locations at the same time. That is he sees a real life scene from the location of his right eye and at the same time sees a similar real life scene from the more left location with his left eye. In real life this occurs naturally. When pictures are substituted for real life, it requires the use of two pictures taken respectively from these different right eye and left eye locations. Furthermore, to see stereoscopic depth perception in these two pictures requires the use of a stereoscope or other system to control which eye sees which picture only.
Psychological depth perception on the other hand can employ the use of only one eye while looking at the real life world. A one-eyed observer perceives depth by the psychological depth perception cues normally present in most real life scenes.
When pictures are substituted for real life, the one-eyed observer simply looks at a single picture and sees depth in the picture by the same psychological depth perception cues.
Following is a list of the most common psychological depth perception cues:
1. Areal perspective, the change of color or softening of the shapes (sometimes called "graying") gives a feeling of distance to far objects.
2. Distribution of light and shade upon an object gives information as to its solidity and shape as, for example, the highlights and shadows of a sphere which make it appear round.
3. Overlapping of contours, as when a near object hides part of a more distant object thereby providing information of their relative distances.
4. Geometrical perspective is an indicator of distance as, for example, the parallel rails of a railroad track appear to converge as they extend in the distance.
5. Depth is sensed by the interpretation of size, because a near object appears larger than a similar object farther away.
All of these psychological depth perception cues are very effective for a one-eyed observer, or a two-eyed observer employing only one eye. However, when two eyes are employed, the binocular stereoscopic depth perception sense of the observer comes into play and, because it is very strong, it tends to override most, if not all, of the aforementioned inherent psychological depth indicators whereby the picture appears to be the flat picture it actually is. That is to say the scene appears to be a flat picture on a flat plane or two dimensional surface.
These psychological depth perception cues are listed on pages 1071 to 1074 of the "Text-Book of Opthalmology", 1946, by Duke-Elder, Volume I. Here also the author makes reference to the fact that Francis Bacon (Englishman who lived 1561 to 1626) pointed out that, ". . . pictures look more realistic when regarded with one eye so that the lack of the stereoscopic effect is not felt psychologically". Bacon's observation is still accepted today.
A better understanding of these principles can be had if the reader takes time at this point to actually experience the difference between one-eyed and two-eyed viewing of flat two dimensional photographs. Looking at several different photographs (not drawings or paintings) on a wall sized calendar, while alternately covering one eye, then uncovering it to use two eyes, will forcefully demonstrate the concept. Upon covering one eye for a few seconds, the observer will gradually see depth in the calendar photograph that he never saw before with two eyes.
Recently while working in a lighted room with images projected onto a focusing concave mirror screen, previously unnoticed visual pehnomena were discovered which later led to this invention. See my U.S. Pat. No. 4,322,747, granted Mar. 30, 1982, and my pending patent application, Ser. No. 478,533, filed Mar. 24, 1983.